A found-footage approach makes it possible for camera and crew to exploit the Paris catacombs, while sacrificing cinematic thrills along the way.

Beneath the streets of Paris lies a vast network of tunnels just waiting to be exploited by an enterprising found-footage film crew. Imagine the excitement of the rolling-boulder opening scene in “Raiders of the Lost Ark” stretched to feature length, then subtract such vital ingredients as John Williams’ pulse-elevating score, Douglas Slocombe’s visceral cinematography and Harrison Ford’s wry charisma, and you get “As Above, So Below,” in which a Lara Croft-like heroine assembles a team of expendable “cataphiles” (as catacomb obsessives call themselves) to locate the Philosopher’s Stone. It all makes for clumsy-fun escapism, not bad as end-of-summer chillers go, but small-time compared with other Legendary releases.

Returning to the faux-doc format they helped innovate in such pics as “The Poughkeepsie Tapes” and “Quarantine,” the Dowdle brothers, John Erick (who directs) and Drew (his fellow producer), are by now experts at creating suspense within narrow confines. Their previous feature, “Devil,” took place almost entirely in an elevator, and considering all the challenges that the Paris catacombs would pose a traditional camera team — low ceilings, narrow passages and waist-deep water — they’ve managed to generate some genuine tension without straying too far from the realm of the real.

That means nearly all the thrills come either from things that could actually happen (claustrophobia, cave-ins and encounters with the various weirdos you might expect to meet underground) or directly from the characters (who all have deaths of friends or family members unresolved in their pasts) — the idea being that venturing down certain corridors of the catacombs is a bit like spelunking in one’s own subconscious. Here, in a calculated yet nevertheless welcome twist on traditional gender roles, it’s a young woman who emerges as the fearless and resourceful leader of the expedition, recruiting a French ruffian named Papillon (Francois Civil) and two of his grungy sidekicks, Souxie (Marion Lambert) and Zed (Ali Marhyar), as guides.

Branching out from a resume consisting mostly of small roles in upscale literary projects, British actress Perdita Weeks plays Scarlet, a woman who will stop at nothing to get to the “truth.” Fluent in six languages and a black belt in karate, this readymade heroine probably came preloaded with the Dowdles’ screenwriting software, taking over her alchemy-expert dad’s search for the Philosopher’s Stone after his suicide. Scarlet doesn’t have many distinguishing characteristics beyond that: no bullwhip, no fear of snakes, just a penchant for spouting exposition and a lingering crush on sometime-sidekick George (“Mad Men’s” Ben Feldman), whose hobby involves breaking into places and fixing old monuments — which is basically the opposite of what this mission of crumbling walls, collapsing ceilings and breaking centuries-old artifacts entails.

Once Scarlet gets going, there’s nothing stopping her, whether it’s infiltrating booby-trapped caves in Iran of dousing museum treasures with flammable compounds in search of clues, and Elliot Greenberg’s jump-cutty editing style keeps the adventure going at roughly the rate of Scarlet’s intellect — which makes her wild “Da Vinci Code” ramblings sound more impressive than they actually are, in much the way the pic’s hermeticist title suggests a dimension that informs little more than murals glimpsed along the way. It’s a shame the film doesn’t give the audience time to try solving some of the puzzles, rather than simply watching her and George go at it, though the pacing eliminates any room to question her split-second impulses.

As the implied dangers start to become real, however, the movie feels as though it’s moving too fast, abandoning fallen team members with no time to mourn (don’t be surprised if your favorite characters don’t make it) and plunging forever forward, even when signs — “Abandon hope all ye who enter here” — call for a modicum of caution. Cheating the geography, the Dowdles create the illusion that, as a feral character called “the Mole” (Cosme Castro) puts it, “the only way out is down,” despite the fact that they’re basically taking us in circles around the same locations. By the end, they want to give the impression that the entire world has been inverted and the group is now climbing upside-down through places they’ve already passed. However, since the real tunnels were used more than soundstages, the gimmick never quite works.

Still, the filmmakers manage to capture the surreal atmosphere of wandering rogue beneath the streets of Paris, where the usual clues humans use to get their bearings (say, locating the Eiffel Tower on the horizon) or judge the time of day (via the position of the sun) are denied, making for a truly disorienting experience. At the same time, the film features an enhanced soundtrack, which compensates for a camera that goes all wobbly whenever anything truly exciting should be happening onscreen, tickling our imagination with the sounds of cracking walls, eerie whispers and distant chants.

The sixth member of Scarlet’s party is her faithful documentarian, Benji (Edwin Hodge), who rigs each of their helmets with HD cams and then spends the rest of his time in a state of panic. Ideally, these camera placements (just above the eyes) would contribute to a relatively subjective viewing experience, and the film does offer a rare chance to see parts of the catacombs not open to the public, though the visuals feel slapdash instead of cinematic — and the film suffers for it, hiding ghostly figures on the edge of the frame instead of taking full advantage of the environment, the way “The Descent” or “Mimic” approached dark and spooky spaces.

When Scarlet finally does uncover the solution to the Philosopher’s Stone — this legend of alchemy rumored to possess healing powers and the ability to turn ordinary objects into gold — the final reveal is unspeakably corny, suggesting that an hour of therapy might have delivered the same advice. For those hoping to find some truly disturbing secrets buried for generations beneath the surface, track down Gary Sherman’s 1972 “Death Line” (aka “Raw Meat”) instead.

Would hardly describe PROWL or FLIGHT OF THE STORKS as upscale literary productions. Perdita is a natural action heroine who occasionally dons a bonnet – not the other way around. As for her intellect, she is an alumna of Roedean and the Courtauld Institute. Check. See her performance as spy/assassin in UK The Three Musketeers. Action plus Bonnet with Crossbow.